Apparatus for controlling emissions of hydrogen sulfide from a system utilizing geothermal steam

ABSTRACT

Certain impure steams, especially those from geothermal sources, are polluted with hydrogen sulfide, ammonia, carbon dioxide, other gases, and finely divided particulate solid matter in a form resembling dust or smoke. These contaminants reduce the efficiency of the steam as a heat transfer fluid, are detrimental to equipment utilizing steam as an energy source, and result in environmental pollution or expensive requirements for limiting the same. Herein apparatus is provided wherein so polluted steam is selectively processed in the gaseous state upstream of said equipment to remove hydrogen sulfide therefrom, with or without removing other pollutants, to recover valuable materials therefrom, and to improve the utility of the steam as an energy source. This is done by means for contacting a flow of the steam with aqueous liquid reactant media consisting essentially of one or more reactive compounds of certain metals which form solid metal sulfide reaction products and which preferably are electropositive with respect to hydrogen. Means are provided for separating the processed steam and whereby valuable materials subsequently may be recovered from said media as useful byproducts. Means are also provided whereby reactant compounds may be recycled and may be regenerated from the metal sulfide reaction products.

This is a division of application Ser. No. 712,170 dated Aug. 6, 1976,(now U.S. Pat. No. 4,123,506 issued Oct. 31, 1978) and is related to afurther division thereof Ser. No. 938,942, filed Sept. 1, 1978 (now U.S.Pat. No. 4,202,864 issued May 13, 1980).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to apparatus for the treatment of impure steamcontaining a minor proportion of gaseous impurities comprising hydrogensulfide and more particularly of such steam from a subterraneous source,e.g. geothermal steam, to extract therefrom hydrogen sulfide and othersubstances contained therein, to improve the utility of the steam as anenergy source, to reduce environmental pollution from usage of suchsteam, to recover valuable byproducts and for other purposes.

2. State of the Art

Steam, including geothermal steam, has been utilized to provide heatenergy and/or mechanical energy by way of heat exchangers and primemovers, e.g. steam engines and turbines, in systems usually constitutingor employing means for condensing the steam from gaseous to liquidphase.

In the use of geothermal steam for such purposes, equipment corrosionand environmental pollution problems have existed because such steamusually contains small proportions of reactive and noxious contaminantsincluding hydrogen sulfide. Hydrogen sulfide, especially in the presenceof moisture, is corrosive to a number of metals used in mechanical andelectrical equipment. Hydrogen sulfide dissolves in water and forms asolution of hydrosulfuric acid, and in the presence of moist air tendsto oxidize and form sulfurous acid and sulfuric acid solutions, and suchsolutions are strongly corrosive to many metals. Furthermore, hydrogensulfide is a noxious gas highly detrimental as a pollutant to theenvironment. Other contaminant substances which may be present ingeothermal steam include carbon dioxide, ammonia, methane, hydrogen andnitrogen, substances comprising boron, mercury and arsenic, and solidparticulate matter, some of which can contribute to said corrosion andpollution problems. Also, it is often found that the molar quantity ofammonia in geothermal steam exceeds two times the molar quantity ofhydrogen sulfide therein.

In practice, geothermal steam driven turbines and related equipment forproducing power have been constructed with special materials intended toresist the corrosive nature of the hydrogen sulfide in the impuregeothermal steam and, after use of such steam, the hydrogen sulfide isemitted to the environment causing pollution thereof. Such emission ofhydrogen sulfide occurs in part in solution in the cooling watereffluent discharged from direct contact condensers and in other part inthe noncondensable off-gases effluent from such condensers discharginginto the atmosphere. Reported efforts to abate such environmentalpollution have been confined (1) to treatment of the hydrogensulfide-containing cooling water effluent with air, usually in thepresence of a dissolved catalyst, to oxidize the hydrogen sulfide insaid effluent to elemental sulfur for subsequent separation anddisposal, and (2) to treatment of the hydrogen sulfide containingcondenser off-gases to oxidize the hydrogen sulfide therein to sulfur orsulfur dioxide, which oxidized form may then be separated by suitableprocessing for subsequent disposal. Such hydrogen sulfide pollutionabatement practices have been found to be expensive, deal only withenvironmental aspects of the power plant effluents, create catalystrecovery and waste sulfur materials collection and disposal problems,and fail to take advantage of the ammonia contained in geothermal steam.

SUMMARY OF THE INVENTION

The principal object of the present invention is to depart frompractices of treating condenser effluents after condensation of watercondensate from contaminated steam in order to control environmentalpollution and instead to provide apparatus to remove hydrogen sulfidecontained in impure steam, more particularly geothermal steam, which maybe selected from the group consisting of steam vented from the earth asvapor, steam separated from a mixture of steam and liquid water ventedfrom the earth, and steam flashed from liquid water vented from theearth prior to its use as an energy source, so as to produce condensereffluents substantially free of hydrogen sulfide thus inhibiting oreliminating the environmental pollution control problems otherwiseexperienced with such effluents. Other objects are to improve thequality of the steam, and to obtain economic and other advantages.

The present invention further recognizes the fact that impure steamand/or geothermal steam may contain not only hydrogen sulfide but alsoother contaminants that can cause environmental problems and reduce theutility of steam as an energy source, and provides means which aim toimprove such utility and to obtain economic and other advantages byextraction of one or more of said other contaminants prior to use of thesteam as an energy source. With these objects in mind the invention aimsto provide, severally and interdependently, methods or processes andapparatus applicable for extracting from a flow of impure steam, e.g.geothermal system, hydrogen sulfide and possibly others of thecontaminants contained therein before putting the steam to use inheating or mechanical equipment and to effect such extraction with onlynegligable reduction of the heat content of the steam and with increasein the efficiency of the steam as a medium for transfer of its energy.

These objects will be readily understood by reference to approximateanalyses of the contaminants present in geothermal steam such as isfound in wells in the California area known as "The Geysers". The steamfrom such a geothermal well may contain about one percent of gaseouscontaminants, or may contain greater or lesser amounts thereof. Thetable below shows reported analyses of the steam from (I) a particularsuch geothermal well and (II) the overall average of more than 60 suchgeothermal wells, approximately in parts per million (ppm):

    ______________________________________                                                        (I)      (II)                                                 ______________________________________                                        Carbon dioxide    8000       3000                                             Ammonia           700        500                                              Hydrogen sulfide  500        500                                              Methane           400        500                                              Nitrogen          300        200                                              Hydrogen          100        200                                              ______________________________________                                    

with less than 100 ppm of other gaseous substances comprising boron,arsenic, mercury and argon. Such geothermal steams also may contain, asanother contaminant, finely divided particulate solid matter in a formresembling dust or smoke particles, and as shown by the analyses areessentially devoid of free oxygen.

The presence of noncondensable gases in the steam reduces its efficiencyas a heat transfer medium and entails otherwise unnecessary expendituresfor power and equipment to accommodate and eject the same. The presenceof finely divided particulate matter in the steam causes harmfuldeposition in, and erosion of, the equipment employing the steam as anenergy source.

Other objects of the present invention are to provide means to furtherincrease the purity of impure steam by extracting other contaminantstherefrom, and/or to recover one or more valuable products or byproductstherefrom, together with improvement of the utility of said steam as anenergy source.

Also, the present invention provides means which aim to remove inreadily separable form by chemical means certain of said contaminantswhich are chemically reactive, so that they may be recovered as valuablebyproducts separate from the non-reactive components, which may then berecovered, if desired, essentially free of contamination by saidchemically active contaminants.

In addition, the present invention provides means which aim toadvantageously employ finely divided particulate material to aid in theremoval of hydrogen sulfide, and in this connection to alsosimultaneously remove from the geothermal steam finely dividedparticulate solid matter carried thereby to further improve the utilityof the steam as an energy source.

As compared with steam conventionally produced from fresh surfacewaters, geothermal steam, which is produced subterraneously at hightemperature and pressure from water far below the surface of the earth,contains higher proportions of the heavy isotopes of the elements ofwater. The applicant has determined that this isotopic relationship, aswell as the natural high temperature of geothermal steam, can beemployed in accordance with the present invention to provide a usefulfeed for heavy water production systems, e.g. as disclosed in copendingapplication Ser. No. 712,171 concurrently herewith and hereinincorporated by reference, with essentially no detriment to the abilityof the geothermal steam to serve as a source of energy as abovedescribed and at considerable economic advantage. This further advantageis attained in accordance with the present invention since the means forpretreatment of the geothermal steam to improve its utility as an energysource may readily be adjusted to also contribute to its utility as adeuterium source for heavy water production at essentially no additionalprocessing cost, with this latter contribution imposing no penalty onthe utility of the steam as an energy source.

In brief, various of the foregoing and other objects and advantages areobtained in accordance with this invention as a result of applicant'sdiscoveries that various contaminants present in geothermal steam,and/or deuterium present therein in greater abundance than in freshsurface water, can be transferred at the temperature and pressure of thesteam to an aqueous liquid; that certain of said contaminants can bechemically reacted in such aqueous liquid to form substances which maybe separated and recovered therefrom; that deuterium in such steam canbe readily exchanged for protium from such aqueous liquid at thetemperature and pressure of the steam; that such transfers and reactionscan take place with essentially no material change other than theimprovement of utility of the geothermal steam; and that they can becarried out in a selective manner which enables recovery of suchdeuterium and/or contaminants in the form of valuable byproductmaterials.

The invention is particularly directed to apparatus for utilizinggeothermal steam wherein prior to such utilization hydrogen sulfide andoptionally other gaseous impurities are removed from the steam bycontacting the steam with an aqueous dispersion of at least one metalcompound which is capable of reacting with the hydrogen sulfide andforming a solid metal sulfide reaction product, for example, an iron,zinc or copper compound, which compound may advantageously be employedalone or in combination with another, and in which the utilization meanscomprises condenser means and means for discharging liquid watersubstantially free of hydrogen sulfide and noncondensable gasessubstantially free of hydrogen sulfide. Preferred embodiments of thesystem employ a compound of a metal which can form a metal sulfide thatis capable of reacting with acid to regenerate the said compound andalso produce hydrogen sulfide that can be recovered, i.e. of a metalhaving an electrode oxidation potential positive with respect tohydrogen in the electromotive series, such a compound being, forexample, zinc sulfate which can be regenerated from zinc sulfide withproduction of hydrogen sulfide by reacting the zinc sulfide withsulfuric acid.

The invention will be most readily understood from the followingdescription of preferred embodiments thereof, which are to be deemedillustrative and not restrictive of the invention, the scope of which ispointed out in the appended claims.

SHORT DESCRIPTION OF THE DRAWINGS

In the accompanying drawings in which flow diagrams are set outillustrative of the invention:

FIG. 1 is a flow diagram of a system according to the invention forextracting hydrogen sulfide from a flow of impure steam containing thesame, with optional provision for prior extraction of ammonium from saidflow,

FIGS. 1a, 1b, 1c and 1d, diagrammatically illustrate various elementsfor contacting steam and liquid employable in the arrangement of FIG. 1,

FIG. 2 is a flow diagram illustrating a modification of a part of thesystem of FIG. 1 for adapting the same to simultaneously extracthydrogen sulfide and ammonia from a flow of steam containing the same,

FIG. 3 is a flow diagram illustrating a modification applicable to thesystems of FIGS. 1 and 2 for subsequently extracting from the flow ofsteam effluent from FIG. 1 or FIG. 2, carbon dioxide contained therein,

FIG. 4 diagrammatically illustrates a modification applicable to any ofthe foregoing systems for the extraction of deuterium from the flow ofsteam effluent therefrom,

FIGS. 5 through 8 diagrammatically illustrate modifications, applicableto those of the foregoing systems in which ammonia is extracted from theflow of steam as an ammonium salt solution, for concentrating andrecovering the ammonium salt values thereof, the modifications of FIGS.6, 7 and 8 including heat economizing provisions,

FIG. 9 diagrammatically illustrates a modification of the system of FIG.7, and

FIG. 10 diagrammatically illustrates a modification of the system ofFIG. 8.

DETAILED DESCRIPTION

In the embodiment of the invention illustrated in FIG. 1, the systemcomprises a method or process and apparatus for treating a gaseous flow110 e.g. from a geothermal source via 110', consisting principally ofsaturated steam at super-atmospheric pressure and containing othergaseous substances for extracting therefrom hydrogen sulfide containedtherein and is particularly but not exclusively adapted for effectingsuch extraction from such a gaseous flow containing less than 1 molarpercent of hydrogen sulfide. Such steams occur as the result ofindustrial processes or naturally as geothermal steam.

In this embodiment there is provided from reactant supply means via 114and/or 114a an aqueous liquid reaction medium carrying dispersedtherein, in solution or suspension, reactant 111 consisting essentiallyof at least one metal compound, the metal of which is selected from theclass of metals having an electrode oxidation potential positive withrespect to hydrogen in the electromotive series, which metal compoundhas the capability of undergoing reaction with aqueous hydrogen sulfideto form a solid metal sulfide reaction product, the metal sulfide ofwhich has, at 25° C., a solubility product smaller than 10×10⁻¹⁵, e.g.compounds of nickel, iron, zinc, etc. Said liquid reaction medium 114may be provided by mixing said reactant 111 with water 112, and heatingand pressurizing the same, in suitable conditioning apparatus 113.

As shown in FIG. 1, means are provided for passing the flow of steamfrom 110 in intimate contact with said aqueous liquid reaction medium114 in extractor 115 which may be reactor, cocurrent and/orcountercurrent, of the wet scrubbing type, e.g. packed-, tray-, orspray-tower, or a venturi, multiple venturi, or other suitable gas andliquid contact device, arranged, e.g. as shown in FIGS. 1a, 1b, 1c, 1d,or otherwise, it being understood that where separate contactingelements are shown such elements may be contained in a common housing.To inhibit condensation of steam from flow 110 in extractor 115, theliquid reaction medium 114 should be delivered into said extractor atapproximately the temperature of the flow of steam 110 therein.

In extractor 115, gaseous hydrogen sulfide from the flow 110 dissolvesin the aqueous liquid phase and reacts with reactant from 111 therein toform one or more solid metal sulfide reaction products. This effectivelyremoves dissolved hydrogen sulfide from the aqueous phase and enablesadditional hydrogen sulfide from the gaseous phase to dissolve therein,progressively, thereby causing the gaseous flow from 110 to becomedepleted in hydrogen sulfide in extractor 115.

The aqueous reaction medium and non-gaseous products of the reaction inextractor 115 are separated by separator means thereof from the gaseousflow and removed as at 116, and the gaseous flow depleted in hydrogensulfide is delivered from extractor 115 as at 110a.

As is schematically illustrated in FIG. 1, the contacting of the aqueousliquid reaction medium from 114 with the flow of steam from 110 inextractor 115 may be effected in any suitable manner, e.g. the gaseousflow may be bubbled through a batch of the aqueous reaction mediumcontained in extractor 115 during the process of extraction, or it maypass in cocurrent or countercurrent contact with the flow from 114 to116 of the aqueous reaction medium. Especially in the latter case, andparticularly where only a part of the reactant comprised in the flowfrom 114 is reacted in the contact before leaving the extractor 115 via116, the illustrative embodiment contemplates recycling to the contactin extractor 115 via 114a all or a part of the unreacted reactant from116. This may be effected via valved conduit 118(b), without firstseparating solid materials therefrom, or via valved conduit 118(c) afterseparation of solids in separator 117. The aforesaid batch operation mayalso be carried out with recirculation of the aqueous reaction medium ina similar manner. For continuous operation, the recirculation via 114amay be combined with the flow from 114 and, if desired, all or a portionof the flow from 116 may be delivered via 119 and/or 120 for furthertreatment as hereinafter described.

Precipitation of solid metal sulfide reaction products in extractor 115may be aided by dispersing in the liquid aqueous reaction medium finelydivided solid particulate matter for acting as substrata for suchprecipitation, this substrata material being removed from extractor 115with the precipitated reaction products as at 116. Such substratamaterial may be added as a slurry to 113, and/or may be carried intoextractor 115 by recycle via 114a of a part of the solids in the liquidin 116, or as a constituent of the gaseous flow 110, and/or may beformed in situ in 115 as by reaction of hydrogen sulfide contained inthe gaseous flow 110 with a second metal compound, supplied to theaqueous liquid in 115, the metal of which is selected from the subclasshaving an electrode oxidation potential negative with respect tohydrogen in the electromotive series and capability of undergoingreaction with aqueous hydrogen sulfide to form a solid second metalsulfide product, e.g. compounds of silver, mercury, arsenic, copper,etc. When a finely divided solid particulate material and/or a secondmetal compound is a constituent of the gaseous flow 110, such materialor compound not only becomes dispersed in the aqueous liquid reactionmedium in 115 to provide such substrata, but in addition the gaseousflow withdrawn via 110a becomes depleted in said solid particulatematerial and/or compound whereby the utility of said gaseous flow isimproved for its subsequent use, e.g. for operating steam turbines, orfor use in chemical processes. Also when the flow 110 of steam, e.g.geothermal steam, also contains in gaseous form a quantity of substancecomprising at least one of the elements of the class consisting ofboron, arsenic and mercury, e.g. compounds of boron, arsenic and mercuryand/or mercury vapor, at least a part of such substance, depending onits partial pressure and/or its reactivity with constituents of theaqueous liquid reaction medium will become dispersed in said aqueousmedium in 115 and be removed as at 116, whereby the resultant steam flow110a from 115 is also depleted in its content of said gaseous substance.

Still referring to FIG. 1, the non-gaseous metal sulfide reactionproducts removed from the extractor at 116 are preferably separated fromthe aqueous liquid medium, as at 117 (although such separation may beomitted, as indicated by the valves 118, 118a in FIG. 1, when theaqueous medium contains no constituent to be excluded from thesubsequent processing illustrated in FIG. 1) and are thereafter passed,as at 120, to reactor 121 where they are treated by adding thereto, via121a, aqueous acid selected from the class of acids capable of reactingwith said at least one metal sulfide to regenerate hydrogen sulfide gastherefrom with formation of metal salt of said acid and hydrogensulfide. Suitable acids for this purpose are the acids more active thanhydrosulfuric acid and non-oxidizing to hydrogen sulfide, e.g. sulfuric,hydrochloric and phosphoric, of which sulfuric is preferred. Followingthe acid treatment in reactor 121, the regenerated hydrogen sulfide gasmay be withdrawn and recovered, as at 122, and the metal salt formed,e.g. metal sulfate, may be withdrawn in, and recovered with or from, theaqueous medium, as at 123.

Where solid particulate matter has been supplied to the aqueous reactionmedium via 110 or otherwise as above described and is inert to the saidacid treatment, then following such treatment the insoluble residue maybe separated in 127 by centrifuging, filtration or other separationmeans. Where such solid particulate matter is not a constituent of thegaseous flow 110, it may be suitably treated and recycled, as via 129,for reuse as substrata as aforesaid.

The metal salt withdrawn at 123 may be delivered to storage or otheruse, e.g. via valved outlet 124, or it may be recycled via 125, 127, 129as a component useful for preparing the aqueous liquid reaction medium114. In the latter case, as indicated in FIG. 1, where the reactantsupplied at 111 is a metal salt and the same metal salt is formed inaqueous solution in reactor 121, such solution may be recycled via theconditioning apparatus 113, as shown at 125-129, with or withoutconcentration or other treatment, as in 127, and used in lieu of a freshsupply of reactant from 111. Or, where the reactant supplied at 111comprises a compound selected from the class consisting of hydratedoxides, hydroxides and carbonates, then the metal salt formed in aqueoussolution in reactor 121 may be chemically converted from the watersoluble salt form to a water dispersible hydroxide or carbonate form, byreaction in 127 of said metal salt formed in aqueous solution with anappropriate base, e.g. sodium hydroxide, sodium carbonate, lime,ammonia, or the like, supplied at 128, for recycling via 129 to 113, theconversion byproducts being withdrawn from 127 as through valved line126.

In the embodiment of FIG. 1, ammonia may optionally be extracted fromthe flow of steam to 110 before subjecting such flow to extraction ofhydrogen sulfide therefrom, in 115, by contacting the flow of steampassing from 110' to 110 in a reactor 130 supplied with aqueous acid via131 to form an aqueous solution of ammonium salt of the acid, thereactor 130, being like the extractor 115 or of any other suitable typeand arranged in any suitable manner, e.g. as in FIGS. 1a, 1b, 1c, 1d, orotherwise. This preliminary removal of ammonia may be accomplished byadjusting the valves 108, 109 to pass the ammonia-containing steam flowthrough 130 before it passes to 115 and enables recovery via 132 of theammonia from 130 free of sulfide contamination as an ammonium salt of anacid selected from the class of acids which are non-oxidizing tohydrogen sulfide and form a water soluble ammonium salt while in contactwith said flow of steam, e.g. sulfuric acid, phosphoric acid,hydrochloric acid, etc., the ammonium salts of the preferred acids beingthose constituting valuable byproducts, e.g. fertilizer constituents.This procedure also has the advantage that it enables the recovery ofmetal sulfides from extractor 115 free from influence of ammonia, andenables employment in 115 of a metal salt of an acid different from theacid employed in 130.

As previously mentioned the reactor 130 and/or extractor 115 may bearranged as shown in FIGS. 1a, 1b, 1c, 1d, or otherwise. For brevity, inthese figures the same numerals as in FIG. 1 are used for the flow ofsteam from 110 to 110a and the flow of liquid from 114 to 116 withrespect to extractor 115, which may be taken as also typifying reactor130. Thus, in FIGS. 1a and 1b, element 115 is illustrated as aconventional gas/liquid contact apparatus, that in FIG. 1(a) being ofthe cocurrent type and that in FIG. 1(b) being of the countercurrenttype. In FIG. 1c, element 115 comprises a plurality of separatecocurrent contact means illustrated as 115c-1 and as 115c-2 throughwhich the steam is passed in series from 110 to 110a, the flow of liquidphase from 114 to 116 passing between 115c-1 and 115c-2 cocurrently withthe flow of steam therebetween. In FIG. 1d, element 115 comprises aplurality of separate cocurrent contact means illustrated as 115d-1,115d-2, and 115d-3 through which the steam flow is passed in series from110 to 110a, the liquid flow from 114 to 116 being passed between 115d-3and 115d-2 and then between 115d-2 and 115d-1 countercurrently to theflow of steam therebetween.

Particularly advantageous arrangements of cocurrent reactors usable at115 and 130 are set forth in my copending application Ser. No. 655,239filed Feb. 4, 1976 entitled "Contact Method and Apparatus for MultiphaseProcessing" (issued as U.S. Pat. No. 4,062,663 dated Dec. 13, 1977), thedisclosure of which is herein incorporated by reference. Thus thedisclosure of this patent includes cocurrent contact apparatuscontaining the previously mentioned separator means.

In the embodiment of FIG. 2, the liquid aqueous reactant supplied via214 to extractor 215 to extract hydrogen sulfide and other gases fromthe steam 210 comprises a liquid aqueous medium carrying a reactant, insolution or dispersion therein, consisting essentially of at least onemetal salt of an acid, the metal component of which is selected asdescribed in connection with FIG. 1, and the acid component of which isselected from the class of acids which in aqueous solution arenon-oxidizing to hydrogen sulfide, have dissociation constants inaqueous solution greater than that of hydrosulfuric acid (H₂ S), andform water soluble ammonium salts, the selection preferably being madeto contribute the desired acid radical for the ammonium compound to beformed by reaction with ammonia from the steam 210 in the extractor 215.A preferred acid radical in this connection is the sulfuric acid orsulfate radical (SO₄ ⁼), as ammonium sulfate is a product of value. Thisliquid aqueous reactant from 214, preferably adjusted in temperature andpressure to conform to those of the steam 210 entering the extractor215, is brought into intimate contact with the flow of steam 210 inextractor 215 (which may be similar in type and arrangement to 115 ofFIG. 1), the insoluble and water soluble materials are removed with theaqueous medium at 216, while the flow of steam depleted in hydrogensulfide and ammonia content is withdrawn or delivered from the extractoras at 210a. In one embodiment of the invention, when the molar quantityof ammonia contained in the flow of impure steam passing to extractor215 is in excess of two times the molar quantity of hydrogen sulfidecontained therein, a quantity of acid of said class sufficient to reactwith at least part of but not more than said excess is also contactedwith said flow of steam. In another embodiment, when the molar quantityof hydrogen sulfide contained in the flow of impure steam passing toextractor 215 is in excess of one-half the molar quantity of ammoniacontained therein, a quantity of basic reagent, e.g., base, sufficientto react with at least a part of but not more than said excess is alsocontacted with said flow of impure steam.

Still referring to FIG. 2 the insoluble metal sulfide and other solidmaterials may be separated from the ammonium salt solution withdrawn at216, as at 217, and the separated ammonium salt solution may bewithdrawn via 219, or for conversion to, a valuable product of theprocess. The insoluble metal sulfide solids, withdrawn from 216 with orwithout separation of liquid therefrom in 217, are delivered at 220, andmay be treated to regenerate the metal salt reactant for 214 in anysuitable way, e.g. as described in connection with the circuit 125, 127,129 of FIG. 1.

Of course, in the arrangement of FIG. 2 the supply and removal orrecycle of substrata substance with respect to 215 may be employed asdescribed with respect to 115 in FIG. 1. Also, in the arrangement ofFIG. 2 the processing of substance comprising boron, arsenic and/ormercury, may be effected as above described with respect to FIG. 1.

In the modification of FIGS. 1 and 2 illustrated in FIG. 3, carbondioxide contained in the impure steam processed in FIGS. 1 or 2, and/orintroduced into the steam in such processing, is removed from the flowof steam to improve its utility as an energy source and/or as adeuterium feed supply for a heavy water concentration process, and toyield as a product of value a substantially pure supply of carbondioxide.

Referring to FIG. 3, impure steam which has been depleted in hydrogensulfide or in hydrogen sulfide and ammonia according to the system ofFIGS. 1 or 2, and which has been discharged as at 110a of FIG. 1 or at210a of FIG. 2, is passed via 310 in contact, and preferablycountercurrent contact, in carbon dioxide extractor 315 (which may besimilar in type and arrangement to 115 of FIG. 1), with an aqueoussolution of carbon dioxide binding material from 314, which material isselected from the class consisting of the water soluble materialscapable of binding carbon dioxide in said aqueous solution at thetemperature and pressure conditions of the contact of the steamtherewith in 315. This class of materials is exemplified by the watersoluble inorganic bases, e.g. alkali and alkaline earth metalhydroxides, organic amines having at least two carbon atoms, and alkalimetal carbonates. Of the said class of carbon dioxide binding materials,those which are capable of releasing the bound carbon dioxide andregenerating the binding material when subjected to an alteration of thesaid temperature and pressure conditions, as in a regenerator 317, arepreferred and enable the released carbon dioxide to be withdrawn via 322and enable the solution of the binding material to be recycled to thecontact in extractor 315 as illustrated by the recycle line 314a leadingfrom the regenerator 317 to the supply line 314a. A conduit 314b may beprovided for drawing off of, or supplying make-up to, the solution in314a. With the arrangements of the processes of FIGS. 1, 2 and 3,contaminant materials in mixture in the steam may be removed separatelyrather than in admixture. Such separately removed contaminant materialsmay be in the chemical forms which exist in the steam or in modifiedchemical forms, e.g. hydrogen sulfide, sulfates, metal sulfide, ammonia,ammonium compounds and carbon dioxide, and each such material whenrecovered essentially free of contaminants is a valuable byproduct ofthe overall process.

As above noted, geothermal steam which contains a greater ratio ofdeuterium to protium than does steam generated from fresh surfacewaters, may be used in accordance with the present invention to supplydeuterium for concentration into heavy water in a heavy water productionplant with essentially no detriment to the utility of the steam as anenergy source. Thus, as illustrated in FIG. 4, the purified geothermalsteam from 410 may be contacted countercurrently in a hydrogen isotopeexchanger 415, which may be similar in type and arrangement to FIGS. 1bor 1d, with liquid water of lesser deuterium content essentially free ofvolatile contaminants and which is supplied to the reactor 415, as via414, at essentially the same temperature and pressure as those of thesteam from 410. Such a water may be the deuterium impoverished watereffluent from a heavy water plant which has been freed of dissolvedvolatile constituents, e.g. the usual deuterium depleted water effluentfrom a dual temperature exchange heavy water plant which is dischargedfrom the hot tower thereof at about 130° C. and then stripped ofvolatiles at a higher temperature. The water of lesser deuterium contentsupplied to 415 via 414 extracts deuterium from the steam from 410having a greater deuterium content, in exchange for protium, and thewater from 415 with its deuterium content so augmented to aconcentration not greater than that at equilibrium with said steam from410, is withdrawn, as at 416, for deuterium feed supply to the heavywater plant while the steam with its so reduced deuterium content isdelivered, as at 410a, for further use. Such utilization of steam as adeuterium feed source may be practiced as disclosed in my aforesaidcopending application Ser. No. 712,171.

Referring now to FIG. 5, in this embodiment of the system of theinvention provision is made for the delivery at 519 to a concentratingsystem comprising an indirect contact evaporator 520 of a solution ofammonium salt, as from 219 of FIG. 2, where it may be concentrated at apressure lower than the pressure of the steam at 210a of FIG. 2 byremoving substantially salt-free water therefrom. In the system of FIG.2, the solids separation at 217 may be effected at such lower pressureunder control of the valve 218 with valve 218a closed, in which eventthe ammonium salt solution in 219 may already be reduced to said lowerpressure, otherwise throttling valve means 521 in the system of FIG. 5may be employed to establish the reduced pressure in the evaporator 520.The heating fluid employed for effecting the evaporation in the indirectcontact heat transfer section of the evaporator 520 is supplied via 522,preferably being a portion of processed geothermal steam depleted inhydrogen sulfide as from 210a of FIG. 2, which is condensed in thecondensing section 523 of the evaporator. The condensate formed in 523is removed at 524 and preferably delivered to the water supply forforming the aqueous medium delivered as via 214 of FIG. 2, e.g. thewater supply 112 of FIG. 1. Inert gases separated in the condensation at523 are removed via 525. The water vapor from the evaporation of theammonium salt solution in 520 is withdrawn via 526 to a suitablecondenser 527 to which coolant is supplied as via 529 and thesubstantially salt-free condensate withdrawn at 528 is also preferablyrecirculated at least in part to the water supply for forming the liquidaqueous reaction medium supplied as via 214 of FIG. 2, e.g. via 112 ofFIG. 1. The illustrated evaporator 520 and condenser 527 areconventional indirect contact heat exchange systems, but the inventioncontemplates use of any suitable evaporating and condensing means whichenables separation and removal of condensate and freed gases. Theconcentrated ammonium salt solution, with or without salt crystalstherein depending on the degree of evaporation effected, is withdrawnfrom the evaporator 520, as via line 530, as a useful product, e.g. as afertilizer material, either directly or after further concentration orcrystalization in a separate apparatus or by recycling.

In the form of FIG. 6 the ammonium salt solution 619 to be concentratedand a flow of carrier gas 640 are passed in contact with each other in afirst zone, shown as comprised in the contact elements 631 of thecontact tower 632, wherein the gas is heated and water is vaporizedthereinto. The so heated and humidified gas is then further heated and afurther quantity of water vapor is added thereto in a second zone 633,shown as located above the first zone in the tower 632. The flow of gasfrom 632 via 633 and 634 is then cooled and condensate of essentiallysalt-free water is formed therefrom in a third zone 635, thesubstantially salt-free water being withdrawn in the form of saidcondensate from said third zone, as via the condensate outlet 636 shownas passing from the cold end of 635, but which may pass from the hotend, the cold end, or any intermediate location of the third zone, asdesired. The heat withdrawn from the gas in the third zne 635 istransferred to said first zone 631 for heating the gas therein, thistransfer being effected via a circulation of ammonium salt solution 637,heated by indirect contact with the gas in the heat exchanger 635 anddelivered to said first zone. In the form shown this circulation ofammonium salt solution is drawn via 638 from the liquid outlet 650 fromthe first zone and is recycled through the first zone after being soheated, and a portion of the circulated liquid from 650 is withdrawn via639 for further concentration by evaporation and crystallization of theammonium salt in an evaporator 620, e.g. of the types described inconnection with evaporator 520 of FIG. 5, from which the furtherconcentrated solution and/or crystals are withdrawn via 630. As shown,the water vapor formed in the evaporation in 620 is passed via 623 tofurther heat the flow of gas and add the further quantity of water vaporthereto in the second zone 633. The cooled gas 641 from the third zone635 is further cooled with further condensate being formed therefrom incooler 642 before it is recirculated to the first zone via 640.

The cooler 642 may be a conventional heat exchanger (not shown) cooledby coolant, e.g. cold water from an outside source, or as shown it maybe a countercurrent direct contact heat exchanger employing acirculation 643-644 of the condensate formed therein which in turn iscooled from an outside source via 645, surplus condensate being removedvia 646.

In the form of FIG. 7, the ammonium salt solution 719 to be concentratedand a flow of carrier gas 740 are mixed and passed cocurrently with eachother in a first zone, shown as comprised in the tube elements 731 ofthe indirect contact heat exchanger 732, which may comprise a singleunit or a plurality of units connected in series, wherein the gas isheated and water is vaporized thereinto from said solution 719increasing its concentration of the salt. The so heated and humidifiedgas is separated from the solution in 729 and said gas delivered via 730is further heated and a further quantity of water vapor is added theretoin a second zone, e.g. by steam injector 733 therein supplied with steamvia 723. The flow of further heated and humidified gas passed from saidsecond zone via 734 is then cooled and condensate of essentiallysalt-free water is formed therefrom in a third zone 735, shown as theshell side of said heat exchanger 732, wherein the flow of gas beingcooled is countercurrent to the flow of liquid and gas being heated inthe tube side 731, the substantially salt-free water being withdrawn inthe form of said condensate from said third zone, as via the condensateoutlet 736 shown as passing from the hot end of the third zone 735 butwhich may pass from the hot end, the cold end or any intermediatelocation of the third zone as desired. The heat withdrawn from the gasin the third zone 735 is transferred by conduction to the first zone 731for heating the gas and liquid therein. The concentrated ammonium saltsolution separated from the gas in 729 is withdrawn via 737 and in wholeor in part may be recycled via 738 through all or part of the first zone731 via 738a and/or 738b, and all or part of the concentrated saltsolution or salt slurry from 737 may be withdrawn via 739 for furtherconcentration or crystallization in an evaporator such as 620 of FIG. 6if desired. Steam from an external source, or the water vapor from suchevaporation adjusted if necessary in pressure, is delivered via 723 foremployment in the steam injector 733. The cooled gas 741 from the thirdzone 735 is further cooled with further condensate being formedtherefrom in cooler 742 before it is recirculated to the first zone via740.

The cooler 742 may be a conventional heat exchanger cooled by coolant,e.g. cooling water from an outside source, or may be a countercurrentdirect contact heat exchanger employing a circulation of the condensateformed therein which in turn is cooled from an outside source, e.g. ofthe type shown at 640-645 of FIG. 6.

In the form of FIG. 8, the ammonium salt solution 819 to be concentratedand a flow of carrier gas 840 are mixed and passed cocurrently with eachother in a first zone, shown as comprised in the tube elements 831 ofthe indirect contact heat exchanger 832, which may comprise a singleunit or a plurality of units connected in series, where the gas isheated and water is vaporized thereinto from said solution 819increasing its concentration of the salt. The so heated and humidifiedgas is further heated and a further quantity of water vapor is addedthereto from said salt solution in a second zone 833 by indirect contactwith a heat exchange fluid, e.g. hot liquid or steam therein, suppliedvia 823 and the gas is thereafter separated from the solution in 829.When steam is used in 823 the condensate therefrom is separately removedvia 824. The flow of further heated and humidified gas passed from saidseparator 829 via 834 is then cooled and condensate of essentiallysalt-free water is formed therefrom in a third zone 842. This coolingand condensation is effected by direct contact heat transfer with arecirculating countercurrent flow of the condensate formed in said thirdzone which recirculation in turn is cooled and transfers its heat to thefirst zone by being passed from 842 via 843 to the shell side 835 ofsaid heat exchanger 832 in countercurrent relation to the liquid and gaspassing in said first zone. The condensate formed in this third zone 842is withdrawn as substantially salt-free water, as via the condensateoutlet 836 shown as passing from the hot end of the third zone 842 butwhich may pass from the hot end, the cold end or any intermediatesection of the third zone as desired.

The concentrated ammonium salt solution separated from the gas in 829 iswithdrawn via 837 and in whole or in part may be recycled via 838through all or part of the first zone 831 via 838a and/or 838b, and allor part of the concentrated salt solution or salt slurry from 837 may bewithdrawn via 839 for further concentration or crystallization in anevaporator such as 620 of FIG. 6 if desired. Steam from an externalsource, or the water vapor from such evaporation adjusted if necessaryin pressure, is delivered via 823 for employment in the indirect contactsteam heater 833. The cooled circulation of condensate passing from heatexchanger 832 is further cooled in indirect contact heat exchanger 841which is supplied with coolant from an external source and such furthercooling of the recirculation serves to further cool and condense vaporfrom the gas passing in the third zone 842 before it is passed via 840to the first zone.

In the modification of FIG. 7 shown in FIG. 9, all elements are the sameas in FIG. 7 except that the steam 723, instead of mixing with the gassupplied via 733 from separator 729 as in FIG. 7, is separately suppliedto a section 735a of the shell side of heat exchanger 732 preceding thethird zone 735 which commences at the point 734a in the shell side of732 where the gas from 730 is introduced. The arrangement of FIG. 9 isadvantageous when the steam via 723 is derived from a source at apressure only slightly above the pressure in the third zone 735 since iteliminates the need for providing higher pressure steam as would berequired by the arrangement of FIG. 7.

In the modification of FIG. 8 shown in FIG. 10, all elements are thesame as in FIG. 8 except that the gas which has been heated andhumidified in the first zone is separated from the liquid solution ofsalt in a separator 829a and further heating and humidification of thegas occurs indirectly by vaporization from the liquid solution which isfurther heated via indirect contact heat exchanger 833a supplied via823a with heating fluid, e.g. hot liquid or steam. The cooled liquid orcondensed steam is removed via 824a. In this embodiment, as in FIG. 8,since the heating fluid transfers its energy by indirect contact heatexchange it is not necessary for the pressure of the heating fluid to beas great as the total pressure of the mixed gases in the second zone, aslong as the temperature of the heating fluid is sufficiently high totransfer heat to the salt solution.

While there have been described herein what are at present consideredpreferred embodiments of the invention, it will be obvious to thoseskilled in the art that modifications, including changes, omissions andsubstitutions, may be made without departing from the essence andprinciple of the invention. It is therefore to be understood that theexemplary embodiments are illustrative and not restrictive of theinvention, the scope of which is defined in the appended claims, andthat all modifications that come within the meaning and range ofequivalency of the claims are intended to be included therein.

I claim:
 1. Apparatus for utilizing a flow of geothermal steam atsuperatmospheric pressure containing noncondensable gases together withhydrogen sulfide as impurities therein, and for producing therefromdischarges of liquid water and of noncondensable gases that aresubstantially free of hydrogen sulfide, which apparatus comprises:(a)reactant supply means for providing an aqueous liquid phase containingreactant dispersed therein having the capability of undergoing reactionwith hydrogen sulfide at the temperature of and in the presence of saidflow of geothermal steam to form a solid metal sulfide reaction productsuspended in said flow of liquid; and liquid flow means, includingconduits, connected from said reactant supply means for providing a flowof said aqueous liquid phase; (b) extractor means having steam andliquid phase inlets and outlets and means for passing said flow ofgeothermal steam at superatmospheric pressure in contact with said flowof aqueous liquid phase and effecting said reaction with hydrogensulfide therein, the liquid phase inlet being connected to said liquidflow means and the steam inlet being connected to receive said flow ofgeothermal steam from a geothermal source; (c) separator means connectedin said extractor means for separating and recovering from said contactthe resulting flow of steam at superatmospheric pressure containingnoncondensable gases but depleted in hydrogen sulfide and the resultingflow of aqueous liquid ane metal sulfide reaction product; (d) deliverymeans, including conduits, connected to said separator means fordelivering said recovered flow of steam at superatmospheric pressure forsaid utilizing; (e) steam utilization means including condenser meansconnected to said delivery means for receiving and utilizing recoveredsteam and for condensing liquid water therefrom; (f) liquid dischargemeans connected to said condenser means for discharging therefrom liquidwater condensate substantially free of hydrogen sulfide; and (g) gasdischarge means connected to said condenser means for dischargingtherefrom noncondensable gases substantially free of hydrogen sulfide.2. Apparatus according to claim 1 in which the means (b) provides forpassing said steam and liquid flows in cocurrent contact.
 3. Apparatusaccording to claim 1 in which the means (b) provides for passing saidsteam and liquid flows in countercurrent contact.
 4. Apparatus accordingto claim 1, wherein said flow of geothermal steam contains a quantity ofsubstance comprising at least one of the elements of the classconsisting of boron, arsenic and mercury, in which said means (b)further comprises means for at least in part dispersing said substancein said liquid phase during said contact therein, and the means (c) alsoprovides for separating said flow of steam depleted in its content ofsaid substance.
 5. Apparatus according to claim 1, wherein said flow ofgeothermal steam also contains ammonia, which apparatus furthercomprises:(h) processing means connected to the source of saidgeothermal steam and to said steam inlet of the means (b) for contactingsaid flow of geothermal steam with an aqueous solution of an acid andforming an ammonium salt essentially non-volatile at the temperature ofsaid flow of steam, and for passing to the means (b) said flow ofgeothermal steam depleted in ammonia.
 6. Apparatus according to claim 1,which further comprises:(h) means connected to the means (c) for formingfrom said metal sulfide reaction product separated in the means (c) saidreactant referred to in the means (a); and (i) means connected to themeans (h) and to the means (a) for employing said reactant formed by themeans (h) in the means (a).
 7. Apparatus according to claim 1, whichfurther comprises:(h) means connected to the means (a) and to a sourceof finely divided solid particulate matter for providing saidparticulate matter from said source and dispersing it in said aqueousliquid phase.
 8. Apparatus according to claim 1, wherein only a part ofthe content of said reactant dispersed in said aqueous liquid phase inthe means (b) is reacted with hydrogen sulfide and after said contacttherein the liquid phase contains unreacted reactant, said apparatusfurther comprising:(h) recycle means connected to said extractor and tosaid reactant supply means for recycling at least a part of saidunreacted reactant to said reactant supply means.
 9. Apparatus accordingto claim 8, wherein said reactant is soluble in said aqueous liquidphase, said apparatus further comprising:(i) means connected to saidseparator means and to said recycle means for separating liquid phasecontaining unreacted reactant from the solid phase and for recyclingsaid separated liquid phase containing unreacted reactant supply. 10.Apparatus according to claim 1, which further comprises:(h) meansconnected to the means (c) for treating said metal sulfide reactionsupply product separated in the means (c) with aqueous acid capable ofreacting therewith to regenerate hydrogen sulfide gas and form metalsalt of said acid and said metal; and (i) means connected to the means(h) for separately removing said regenerated hydrogen sulfide gas andsaid metal salt.
 11. Apparatus according to claim 10, wherein said means(i) provides for removing said metal salt in aqueous solution. 12.Apparatus according to claim 10, which further comprises:(j) meansconnected to the means (c) for removing aqueous liquid from said metalsulfide reaction product before the treatment thereof by the means (h).13. Apparatus according to claim 10, which further comprises:(j) meansconnected to the means (i) and to the means (a) for employing metal saltremoved by the means (i) as a source for reactant provided by the means(a).
 14. Apparatus according to claim 13, which further comprises:(k)conversion means connected to the means (j) for chemically convertingmetal salt removed in the means (i) to form said reactant.
 15. Apparatusaccording to claim 1, wherein said flow of steam passing in the means(b) also contains ammonia and the means (a) provides reactant whichconsists essentially of a metal salt which also reacts in the means (b)with said ammonia to form an ammonium salt in said aqueous liquid phasetherein, and in which the means (c) further provides for separating andrecovering the said resulting flow of steam depleted in both hydrogensulfide and ammonia.
 16. Apparatus according to claim 15, which furthercomprises:(h) means connected to the means (b) for providing a quantityof basic reagent to the flows in contact therein.
 17. Apparatusaccording to claim 16, wherein the means (h) provides a quantity ofammonia.
 18. Apparatus according to claim 15, wherein said ammonium saltis in solution in said aqueous liquid phase, which further comprises:(h)means connected to the means (c) for separating and removing the metalsulfide reaction product from the ammonium salt solution.
 19. Apparatusaccording to claim 18, which further comprises:(i) means connected tothe means (h) for reacting said separated metal sulfide in an aqueoussolution of acid for causing hydrogen sulfide and said metal salt to beformed; (j) means connected to the means (i) for separating saidhydrogen sulfide and said metal salt; and (k) means connected to themeans (j) and to the means (a) for recycling said separated metal saltto the means (a).
 20. Apparatus according to claim 18, which furthercomprises:(i) means connected to the means (h) for reacting saidseparated metal sulfide and forming said metal salt; (j) means connectedto the means (i) for separating said metal salt formed therein; and (k)means connected to the means (j) and to the means (a) for recycling saidseparated metal salt to the means (a).
 21. Apparatus according to claim18, which further comprises:(i) means connected to the means (h) forconcentrating said ammonium salt solution separated in the means (h) byremoving substantially salt-free water therefrom.
 22. Apparatusaccording to claim 21, which further comprises:(j) means connected tothe means (i) and to the means (a) for recirculating at least a part ofsaid substantially salt-free water to the means (a).